Laser analytical instrument, laser analytical method, and gas leak inspection instrument

Abstract

Laser light generated from laser light generating means ( 10 ) is fed through laser light transfer means ( 11 ) including a demagnification optical system ( 23 ) so as to be condensed in a part Ex where an object gas of analysis exists. The laser light is imparted with energy for causing a multiple photon excitation phenomenon or a multiple photon ionization phenomenon of gas in the condensed part Ex. The energy of the laser light is large enough for 17 eV or higher energy to be injected into a hydrogen molecule when the object gas of analysis is hydrogen and for 23 eV or higher energy to be injected into a helium atom when the object gas of analysis is helium. For example, the intensity of the laser light in the condensed part Ex is 10 14 W/cm 2 or higher. This provides a laser analytical instrument capable of observing various types of gas through an inexpensive and simple arrangement.

1. A laser analytical instrument for producing fluorescence having a wavelength corresponding to the type of object gas of analysis by exciting the object gas of analysis by laser light and then analyzing the state of the object gas of analysis on the basis of the state of the fluorescence, the laser analytical instrument comprising:
 laser light generating means for generating a single laser light having a given wavelength and top-hat type power density distribution; 
 a demagnification optical system for emitting the laser light generated by the laser light generating means toward an area where the object gas of analysis exists so as to be condensed into a point in the area where the object gas of analysis exists; 
 a phase conjugation laser transfer optical system provided in an optical path of the laser light from the laser light generating means to the demagnification optical system; and 
 fluorescence analysis means for analyzing the state of the received fluorescence, the received fluorescence being produced from the object gas of analysis in the condensed part of the laser light, 
 wherein, when the object gas of analysis comprises hydrogen, the laser light is imparted with energy that injects 17 electron-volts or higher energy into each of one or more hydrogen molecules of the object gas to cause a multiple photon ionization phenomenon or a multiple photon excitation phenomenon of the one or more hydrogen molecules to produce fluorescence in a visible light region from the one or more hydrogen molecules. 
 
   
   
     2. The laser analytical instrument according to  claim 1 , wherein a peak intensity in the condensed part of the laser light is 10 14  W/cm 2  or higher. 
   
   
     3. A gas leak inspection instrument for inspecting an inspection object having a gas passage inside for a gas leak by using the laser analytical instrument according to  claim 1 , the gas leak inspection instrument comprising means for supplying hydrogen to the inside of the inspection object, wherein the laser light is emitted from the demagnification optical system in such a way that the condensed part of the laser light exists in the vicinity of the inspection object in the supply state of the hydrogen, and detects whether there is a leak of hydrogen from inside of the inspection object to outside of the inspection object. 
   
   
     4. The gas leak inspection instrument according to  claim 3 , wherein the inspection object is a fuel cell stack, a hydrogen supply system for supplying hydrogen to the fuel cell stack, or a hydrogen discharge system for discharging the hydrogen from the fuel cell stack. 
   
   
     5. The gas leak inspection instrument according to  claim 3 , wherein when hydrogen is supplied to the inspection object, the laser light is emitted toward the vicinity of the inspection object at least in the state where the inspection object is housed in a closed chamber filled with nitrogen. 
   
   
     6. The gas leak inspection instrument according to  claim 3 , further comprising moving means for relatively moving the condensed part of the laser light with respect to the inspection object. 
   
   
     7. The gas leak inspection instrument according to  claim 6 , wherein the fluorescence analysis means includes means for generating image data indicating a relation between a relative position of the condensed part of the laser light with respect to the inspection object and the intensity of fluorescence having a wavelength corresponding to hydrogen in the fluorescence produced in the condensed part. 
   
   
     8. A laser analytical method for producing fluorescence having a wavelength corresponding to the type of object gas of analysis by exciting the object gas of analysis by single laser light, and then analyzing the state of the object gas of analysis on the basis of the state of the fluorescence, the laser analytical method comprising the steps of:
 providing a phase conjugation laser transfer optical system in an optical path of the laser light from laser light generating means to demagnification optical system; 
 emitting the single laser light having a given wavelength and top-hat type power density distribution toward an area where the object gas of analysis exists so as to condense the laser light into a point in the area where the object gas of analysis exists; 
 when the object gas of analysis comprises hydrogen, causing a multiple photon ionization phenomenon or a multiple photon excitation phenomenon of one or more hydrogen molecules of the object gas using the single laser light imparted with energy that injects 17 electron-volts or higher energy into each of the one or more hydrogen molecules to cause a multiple photon ionization phenomenon or a multiple photon excitation phenomenon of the one or more hydrogen molecules to produce fluorescence in a visible light region from the one or more hydrogen molecules; and 
 receiving the produced fluorescence and analyzing the state of the fluorescence. 
 
   
   
     9. The laser analytical method according to  claim 8 , wherein a peak intensity in the condensed part of the laser light is 10 14  W/cm 2  or higher. 
   
   
     10. A gas leak inspection instrument for inspecting an inspection object for a gas leak, the inspection object being a fuel cell stack, a hydrogen supply system for supplying hydrogen to the fuel cell stack, or a hydrogen discharge system for discharging the hydrogen from the fuel cell stack, the gas leak inspection instrument comprising:
 laser light irradiation means for emitting at least one beam of laser light toward the vicinity of the inspection object; 
 means for supplying hydrogen to the inside of the inspection object; and 
 analysis means for analyzing the state of a received light and detecting whether there is a leak of hydrogen from inside of the inspection object to outside of the inspection object, the received light being generated in the vicinity of the inspection object in the state where hydrogen is supplied to the inspection object, wherein the laser light is imparted with energy that injects 17 electron-volts or higher energy into each of the one or more hydrogen molecules to cause a multiple photon ionization phenomenon or a multiple photon excitation phenomenon of the one or more hydrogen molecules to produce fluorescence in a visible light region from the one or more hydrogen molecules. 
 
   
   
     11. The gas leak inspection instrument according to  claim 10 , further comprising moving means for relatively moving the irradiated position of the laser light with respect to the inspection object. 
   
   
     12. The gas leak inspection instrument according to  claim 11 , wherein the fluorescence analysis means includes means for generating image data indicating a relation between a relative position of the laser light irradiated position with respect to the inspection object and the intensity of light having a wavelength corresponding to hydrogen in the light produced in the condensed part. 
   
   
     13. A laser analytical instrument for producing fluorescence having a wavelength corresponding to the type of object gas of analysis by exciting the object gas of analysis by laser light and then analyzing the state of the object gas of analysis on the basis of the state of the fluorescence, the laser analytical instrument comprising:
 laser light generating means for generating a single laser light having a given wavelength and top-hat type power density distribution; 
 a demagnification optical system for emitting the laser light generated by the laser light generating means toward an area where the object gas of analysis exists so as to be condensed into a point in the area where the object gas of analysis exists; 
 a phase conjugation laser transfer optical system provided in an optical path of the laser light from the laser light generating means to the demagnification optical system; and 
 fluorescence analysis means for analyzing the state of the received fluorescence, the received fluorescence being produced from the object gas of analysis in the condensed part of the laser light, 
 wherein, when the object gas of analysis comprises helium, the laser light is imparted with energy that injects 23 electron-volts or higher energy into each of one or more helium molecules of the object gas to cause a multiple photon ionization phenomenon or a multiple photon excitation phenomenon of the one or more helium molecules to produce fluorescence in a visible light region from the one or more helium molecules. 
 
   
   
     14. A laser analytical method for producing fluorescence having a wavelength corresponding to the type of object gas of analysis by exciting the object gas of analysis by single laser light, and then analyzing the state of the object gas of analysis on the basis of the state of the fluorescence, the laser analytical method comprising the steps of:
 providing a phase conjugation laser transfer optical system in an optical path of the laser light from laser light generating means to demagnification optical system; 
 emitting the single laser light having a given wavelength and top-hat type power density distribution toward an area where the object gas of analysis exists so as to condense the laser light into a point in the area where the object gas of analysis exists; 
 when the object gas of analysis comprises helium, causing a multiple photon ionization phenomenon or a multiple photon excitation phenomenon of one or more helium molecules of the object gas using the single laser light imparted with energy that injects 23 electron-volts or higher energy into each of the one or more helium molecules to cause a multiple photon ionization phenomenon or a multiple photon excitation phenomenon of the one or more helium molecules to produce fluorescence in a visible light region from the one or more helium molecules; and 
 receiving the produced fluorescence and analyzing the state of the fluorescence. 
 
   
   
     15. A gas leak inspection instrument for inspecting an inspection object for a gas leak, the inspection object being a fuel cell stack, a hydrogen supply system for supplying hydrogen to the fuel cell stack, or a hydrogen discharge system for discharging the hydrogen from the fuel cell stack, the gas leak inspection instrument comprising:
 laser light irradiation means for emitting at least one beam of laser light toward the vicinity of the inspection object; 
 means for supplying helium to the inside of the inspection object; and 
 analysis means for analyzing the state of a received light and detecting whether there is a leak of helium from inside of the inspection object to outside of the inspection object, the received light being generated in the vicinity of the inspection object in the state where helium is supplied to the inspection object, wherein the laser light is imparted with energy that injects 23 electron-volts or higher energy into each of the one or more helium molecules to cause a multiple photon ionization phenomenon or a multiple photon excitation phenomenon of the one or more helium molecules to produce fluorescence in a visible light region from the one or more helium molecules.